1. Field of the Invention
Aspects of the present invention relate to a thin film transistor and a flat panel display device including the same, and more particularly, to a thin film transistor including a channel layer including an amorphous 12CaO.7Al2O3 (C12A7), and a flat panel display device including the same.
2. Description of the Related Art
A field effect transistor is an active device including a gate electrode, source electrode, and a drain electrode, and is operated by applying a voltage to the gate electrode to control a current flowing between the source and drain electrodes. In particular, a field effect transistor using a thin film as a channel layer on an insulating substrate formed of ceramic, glass, or plastic is referred to as a thin film transistor (TFT).
Because TFTs use a thin film technology, they can be easily formed on a substrate with a relatively large surface area, and are widely used as driving units of flat panel display devices, such as liquid crystal displays (LCDs). That is, image pixels can be turned on or off using TFTs formed on the substrate. In particular, it is predicted that pixel currents can be efficiently controlled by TFTs in future high-performance organic light-emitting devices. Moreover, a TFT circuit driving and controlling the entire image can be formed on the substrate around the image display region, thereby providing a high performance LCD device.
The most widely used form of TFT uses a polycrystalline silicon film or an amorphous silicon film as a channel layer material. Such a TFT is disclosed in Korean Patent Laid-open Publication No. 1997-0013427. However, in the case of an amorphous silicon or a polycrystalline silicon, a high temperature process is required, and it is difficult to form films of such materials on a plastic or a film substrate.
Organic semiconductor films, such as pentacene, are being developed as a material that can form a film on a plastic substrate at a low temperature. Such organic semiconductors have an aromatic ring, and a large carrier mobility is obtained from the stacking direction of the aromatic ring when crystallized. However, organic semiconductors, such as pentacene, are generally not stable in higher temperatures. An ohmic contact between the source and drain electrode-forming material and the organic semiconducting layer-forming material of a conventional thin film transistor is almost impossible, due to the work function difference between them. Moreover, source and drain electrodes are conventionally composed of inorganic materials, while an organic semiconducting layer is composed of organic materials, and thus the adhesive force between the source/drain electrodes and the organic semiconducting layer is not satisfactory.